Matte photoconductive layers for use in electrophotography

ABSTRACT

POLYMERIC BEADS OF POLY(METHYL METHACRYLATE) OR POLYETHYLENE INCORPORATED IN THE PHOTOCONDUCTIVE LAYER OF AN ELECTROPHOTOGRAPHIC ELEMENT PROVIDE A MATTE PHOTOCONDUCTIVE SURFACE WITH GOOD WRITING CHARACTERISTICS AND ONE WHICH RESISTS IMAGE OFFSET OR SMEARING DURING DEVELOPMENT.

3,810,759 MATTE PHOTOCONDUCTIVE LAYERS FOR USE IN ELECTROPHOTOGRAPHY Richard W. Stahr and Theodore H. Morse, Rochester,

Y1$signors to Eastman Kodak Company, Roches- No Drawing. Continuation-impart of abandoned application Ser. No. 110,339, Jan. 27, 1971. This application Nov. 10, 1971, Ser. No. 197,488

Int. Cl. G03g 5/06 U.S. Cl. 96-1.5 8 Claims ABSTRACT OF THE DISCLOSURE Polymeric beads'ol poly( methyl methacrylate) or polyethylene incorporated in the photoconductive layer of an electrophotographic element provide a matte photoconductive surface with good writing characteristics and one which resists image offset or smearing during development.

This is a continuation in part application based on Stahr and Morse US. application Ser. No. 110,339, filed Jan. 27, 1971 now abandoned.

This invention relates to electrophotography and more particularly to novel matte-surfaced photoconductive elements.

Electrophotographic processes employ an electrophotographic or photoconductive element comprising a coating of a photoconductive insulating material on a conductive support. The element is given a uniform surface charge in the dark and then is exposed to an image pattern of activating electromagnetic radiation such as light or X- rays. The charge on the photoconductive element is dissipated in the illuminated are-a to form an electrostatic charge pattern which is then developed by contact with an electroscopic marking material. The marking material or toner, as it is also called, whether carried in an insulating liquid or in the form of a dry powder, deposits on the exposed surface in accordance with either the charge pattern or the discharge pattern, as desired. Then, if the photoconductive element is of the nonreusable type, the developed image is fixed by fusion or other means to the surface of the photoconductive element. If the ele ment is of the reusable type, e.g., a selenium-coated drum, the image is transferred to another surface such as paper and then fixed to provide a copy of the original.

All of this is well-known and has been described in many patents and other literature, for example, in the patent of Carlson, U.S. 2,297,691, and in more recent works such as Electrophotography by R. M. Schaflert, published by Focal Press Ltd., 1965.

The photoconductive compounds that have been used in electrophotographic processes have included both organic and inorganic compounds. The organic photoconductors have been desirable for a number of reasons. For instance, the organics are less abrasive than the inorganics. They can be charged to high negative or positive potential while the inorganics often saturate at low potential and accept only a positive or a negative charge. In addition the organics usually offer greater exposure latitude, can be spectrally sensitized more effectively and olfer a number of other advantages over zinc oxide and other inorganics.

However, one disadvantage of the use of organic photoconductors has been that the photoconductive layers formed by coating a blend of a binder resin and an organic photoconductive compound have had very smooth surfaces. This has presented problems with respect to the nonreusable types of photoconductive elements such as those comprising a paper support coated with a photoconductive layer. One problem has been that the coatings are so smooth that they are not satisfactory for writing "United States Patent 0 purposes. As compared with inorganic photoconductive layers, such as those containing zinc oxide which are relatively rough, the organic layers are so smooth that they cannot properly be written on by pen or pencil. Even when suitable for certain kinds of writing implements the surfaces are often so smooth that another problem occurs, the problem of smearing or offsetting of the toner image. Thus there has been a need for a matte-surfaced organic photoconductive element which can be written on easily and which is resistant to image offset and smearing or spreading of toner during and after development of the electrophotographic image. There has also been a need for such an element which is relatively free of defect spots which occur when conventional photographic matting agents are incorporated in a photoconductive element.

Still another disadvantage of many otherwise desirable organic photoconductors is that they do not produce images of equal quality with both negative and positive charging. An Advantage of the photoconductive elements of the invention is that the matting agent employed in accordance with the invention enables one to obtain an electrophotographic image of approximately equal quality by either negative or positive charging.

Previous smooth surfaced photoconductive elements when used in simultaneous charging and exposing processes typically required the use of receiving elements which contained spacing particles as described in Gramza and Robinson US. Pat. No. 3,519,819. Thus, the expendable receiver was often relatively costly. By incorporating suitable spacing particles into the reusable photoconductive element of such a process, the cost of the receiver can be reduced.

It is, therefore, an object of the present invention to provide a matte-surfaced photoconductive element. It is a still further object to provide said matte surface using photoconductive element with a surface having good certain polymeric beads.

It is still a further object to provide a nonreusable writing characteristics.

A still further object is to provide a nonreusable photoconductor with a roughened surface from which the toner image will not offset or smear excessively during or after development.

Yet another object of this invention is to provide reusable roughened photoconductive elements suitable for use in simultaneous charging and exposing processes.

In accordance with the present invention, we have discovered that by incorporating certain bead polymers in the binder composition containing the photoconductive compound or coated over said photoconductive layer, an improved product is obtained which has a matte surface suitable for writing and other purposes. Thus, the photoconductive elements of the present invention, in general, comprise an electrically conductive support having coated thereon a layer of insulating binder compound admixed with a photoconductor and a matting agent comprising polymeric beads which are insoluble in the binder solvent and which are electrically homogeneous with respect to the binder-photoconductor mixture. That is, the matting agent has electrical properties similar to those of the binder-photoconductor mixture. Consequently, the matting agent accepts or repels the electroscopic marking material substantially the same as the photoconductorbinder mixture and reduces or eliminates the occurrence of defect spots of either high or low density which have occurred with previous attempts to incorporate matting agents in the photoconductive layers.

Suitable polymeric bead materials include, for example, beads of polymethyl(methacrylate) which are wellknown in the art and can be prepared in sizes ranging in diameter from one to twenty microns by the methods disclosed in US. Pat. 2,701,245.

Another suitable polymeric bead material is polyethylene. Examples of a polyethylene of this kind are the microfine polyethylene powders supplied by U.S.I. Chemicals under the trademark Microthene FNSOO and FN510. These are low-density polyethylene powders of which the particles are spherical and have average diameters of 8 to 30 microns. Typical properties of these materials are, for Microthene FN500 and FNS 10, respectively: melt index (g./l min.) 22 and density (g./cm. 0.915 and 0.924; Vicat softening temperature C.) 81 and 97; and average particle size (microns) 20 and 30.

Particulate material with characteristics unsuitable for use in this invention include, for example, beads or granules of polystyrene, starch, titanium dioxide, silicon dioxide, zinc oxide, lead oxide, aluminum oxide, molecular sieves, clay and talc. Some are unsuitable because they do not form a satisfactory matte and therefore do not reduce toner offsetting. Toner offsetting can be reduced by many of these matting agents as compared with a smooth surface, but tests have shown that their overall results are clearly inferior to those for the polymeric bead matte of the invention, for example, with respect to charge acceptance and sensitometric speed. As a consequence, many of these materials tend to form either high or low density spots which detract from the quality of the electrophotographic image. These materials are, however, useful as spacing or roughening particles for use in reusable photoconductive elements suitable for use in simultaneous charging and exposing processes. All of the polymeric materials mentioned previously are especially well suited for use in elements of this latter type.

The diameter of the matting agent particles or beads can be from about 0.5;; to about 50,u, with the preferred diameter range being from 5 to 40 The choice of particle size is governed in part by the coating thickness of the photoconductive layer, and in part by the degree of roughness desired for ease of writing.

Coating thicknesses of the photoconductive composition on a support can vary widely. Normally, a coating in the range of about 1,u to about 500,14 after drying is useful for the practice of this invention. The preferred range of coating thickness is found to be in the range from about Sp. to about 200 after drying although useful results can be obtained outside of this range.

The percent of matting agent in the photoconductive layer can be from about 0.5 percent to about 30 percent of the total binder-photoconductor composition and preferably is from 1.0 percent to 25 percent. The matting agent should be uniformly dispersed in the photoconductor composition so that the entire layer has homogeneous photoconductive properties.

Although the use of selected matting agents in accordance with the present invention is most applicable to non-reusable photoconductive elements, for example, those having a paper support, it should be understood that the invention extends also to reusable photoconductrve elements, such as used in the process described in U.S. 2,825,814. With such elements, although writability s not a requirement, the improved image quality resultmg from development with the novel matte surface is a significant advantage.

A correlation has been found to exist between quality of the image and the texture of the surface of the photoconductor of this invention as measured in terms of Sheffield Smoothness Value. Best quality is obtained if the Sheffield Smoothness of the element of the invention is about 45 to 300 and preferably 80 to 200.

Sheffield Smoothness Value is a measure of paper smoothness which conforms to Tappi Standard No. T- 479SM48. The equipment for making the measurement is made by Sheffield Corporation, Dayton, Ohio. Briefly, the components of the equipment are (l) a precision device in which the paper sample is held against a smooth glass plate under an accurately weighted, precision-machined head through which regulated air flows; and (2) a Modular Precision Instrument which measures the flow of air across the surface of the paper sample. Data are read in numerical units from 0 (smooth) to 400 (rough). The photoconductive layers and other layers of the element employed as described herein can be coated on a wide variety of conducting supports, which advantageously are flexible, sheet-like materials. Paper is the preferred support although other useful supports include cellulose nitrate film, cellulose ester film, poly(vinyl acetal) film, polystyrene film, polyester, e.g., poly(ethy1ene terephthalate) film, polycarbonate film and related films of resinous materials, as well as glass, metal foils and the like.

" The photoconductors employed in the elements of our invention can be essentially any of the organic photoconductors which are suitable for use in electrophotography.

Examples of the broad class of organic photoconductors include the following:

A. Arylamine photoconductors including substituted and unsubstituted arylamines, diarylarnines, nonpolymeric triarylamines and polymeric triarylamines such as those described in U.S. Pats. 3,240,597 and 3,180,730.

B. Photoconductors represented by the formula where Z and Z' are aromatic radicals, Q is a hydrogn atom or an aromatic amino group, such as ZNH; b is an integer from 1 to about 12, and L is a hydrogen atom or an aromatic radical, these materials being more fully described in U.S. Pat. 3,265,496.

C. Polyarylalkane photoconductors including leuco bases of diaryl or triarylmethane dye salts, 1,1,1-triarylalkanes wherein the alkane moiety has at least two carbon atoms and tetraarylmethanes having an amino group substituted in at least one of the aryl nuclei attached to the alkane and methane moieties of the latter two classes of photoconductors which are nonleuco base materials; and also other polyarylalkanes included by the formula:

wherein each of D, E and G is an aryl group and J is a hydrogen atom, an alkyl group, or an aryl group, at least one of D, E and G containing an amino substituent, these materials being more fully described in U.S. Pat. 3,274,000, French Pat. 1,383,461 and in U.S. Ser. No. 627,857, filed Apr. 3, 1967 by Seus and Goldman now Pat. No. 3,542,544 issued Nov. 24, 1970.

D. Photoconductors comprising 4-diarylamino substituted chalcones having the formula:

wherein R and R are each phenyl radicals including substituted phenyl radicals, these materials being more fully described in Fox application U.S. Ser. No. 613,- 846, filed Feb. 3, 1967 now Pat. No. 3,526,501 issued Sept. 1, 1970, and other chalcones as disclosed in U.S. 3,265,597.

E. Nonionic cycloheptenyl compounds which may be substituted with substituents such as aryl, hydroxy, azido, nitrogen heterocycles, or oxycycloheptenyl; these compounds being more fully described in U.S. Ser. No. 654,091, filed July 18, 1967 now Pat No. 3,533,786 issued Oct. 13, 1970.

F. Compounds containing an NN nucleus, including N,N-bicarbazyls and tetra-substituted hydrazines, which compounds are more fully described in U.S. Ser.

\J No. 673,962 filed Oct. 9, 1967 now Pat. No. 3,542,546 issued Nov. 24, 1970.

G. Organic compounds having a 3,3'-bis-aryl-2-pyrazoline nucleus which is substituted in either five-member ring with the same or different substituents. These organic photoconductors are more fully described in U.S. Ser. No. 664,642 filed Aug. 31, 1967 now Pat. No. 3,527,602 issued Sept. 8, 1970.

H. Triarylamines in which at least one of the aryl radicals is substituted by an active hydrogen-containing group or a vinyl or vinylene radical having at least one active hydrogen-containing group. These materials are more fully described in U.S. Ser. No. 706,780 filed Feb. 20, 1968 now Pat. No. 3,658,520 issued Apr. 25, 1972.

I. Organo-metallic compounds having at least one aminoaryl substituent attached to a Group IVa or Group Va metal atom such as silicon, germanium, tin and lead from Group We and phosphorus, arsenic, antimony and bismuth from Group Va. These materials can be substituted in the metallo nucleus with a wide variety of substituents but at least one of the substituents must be an amino-aryl radicals. These materials are described in U.S. Ser. No. 650,664 filed July 3, 1967 now Pat. No. 3,647,429 issued Mar. 7, 1972.

I. Polymeric organic photoconductors such as poly-N- vinylcarbazoles and related vinyl polymers, such materials being disclosed, for example, in U.S. 3,037,861, U.S. 3,155,503, U.S. 3,418,116, U.S. 3,421,891 and U.S. 3,232,755.

K. Any other organic compound which exhibits photoconductive properties such as those set forth in Australian Pat. 248,402.

Representative organic photoconductors useful in this invention include the compounds listed below:

triphenylamine 4,4'-diethylamino-2,2'-dimethyltriphenylmethane 4,4"-diamino-4-dimethylamino-2,2"-dimethyltriphenylmethane 4', "-bis(diethylamino)-2,6-dichloro-2',2"-dimethyltriphenylmethane 2',2.-dimethyl-4,4,4"-tris(dirnethylamino)-triphenylmethane 4',4-bis(diethylamino)-4-dimethylamino-2,2',2"-

trimethyltriphenylmethane 4,4"-bis(dimethylamino)-2',2"-dimethyl-4-methoxytriphenylmethane bis (4-diethylamino)tetraphenylmethane 4,4-bis(diphenylamino)chalcone tetra-4-tolylhydrazine poly-N-vinylcarbazole monobrominated poly-N-vinylcarbazole dibrominated poly-N-vinylcarbazole N,N-bicarbazyl 3,3 '-bis( 1,5-diphenyl-2-pyrazoline 1,5-diphenyl-3-[3'-(1'-tolyl-5'-phenyl)-2'-pyrazolyl] 2-2-pyrazoline p-diphenylaminostyrene p-diphenylaminocinnamic acid triphenyl-p-dimethylaminophenylstannane triphenyl-p-diethylaminophenylplumbane tetra-p-diethylaminophenylplumbarie phenyl-tri (p-diethylaminophenyl stannane tetra-p-diethylaminophenylgermane p-diethylaminophenylarsine.

Although some polymeric organic photoconductors can be coated on a support without being blended with resinous binder materials it is usually necessary or at least desirable to blend organic as well as inorganic photoconductors with a resinous or plastic material which serves as a matrix or binder for coating the photoconductor on its support. The photoconductive element or layer thus would include both the active organic or inorganic photoconductor and the resinous binder, if one is used.

Preferred binders for use in preparing the present photoconductive layers are film-forming, polymeric binders having fairly high dielectric strength which are good electrically insulating film-forming vehicles. Materials of this type comprise styrene-butadiene copolymers; silicone resins; styrene-alkyd resins; silicone-alkyd resins; soya-alkyd resins; poly(vinyl chloride); poly(vinylidene chloride); vinylidene chloride acrylonitrile copolymers; poly(vinyl acetate); vinyl acetate-vinyl chloride copolymers; poly- (vinyl acetals), such as poly(vinyl butyral); polyacrylic and methacrylic esters, such as poly (methyl methacrylate) poly(n-butyl methacrylate), poly(isobutyl methacrylate), etc.; polystyrene; nitrated polystyrene; poly(methyl styrene); isobutylene polymers; polyesters, such as copoly- [ethylene co alkylenebis(alkyleneoxyaryl)phenylenedicarboxylate] e. g., poly[ethylene-co-isopropylidene-2,2-bis- (ethyleneoxyphenyl)terephthalate] phenolformaldehyde resins; ketone resins; polyamides; polycarbonates; polythiocarbonates; copolymers of vinyl haloarylates and vinyl acetate such as poly(vinyl-m-bromobenzoate-co-vinyl acetate); waxes and chlorinated polyethylene.

Solvents useful for preparing coating compositions with the photoconductors of the present invention can include a wide variety of organic solvents for the components of the coating composition. For example, benzene; toluene; acetone; Z-butanone; chlorinated hydrocarbons such as methylene chloride, ethylene chloride and the like; ethers, such as tetrahydrofuran and the like, or mixtures of such solvents can advantageously be employed in the practice of this invention.

In preparing the coating compositions useful results are obtained where the photoconductor substance is an amount equal to at least about 1 weight percent of the coating composition. The upper limit in the amount of photoconducor substance present can be widely varied in accordance with the usual practice. In those cases where a binder is employed, it is normally required that the photoconductor substance be present in an amount from about 1 weight percent of the coating composition to about 99 weight percent of the coating composition. A preferred weight range for the photoconductor substance in the coating composition is from about 10 weight percent to about 60 weight percent.

Sensitizing compounds useful with the photoconductive elements of the present invention can be selected from a wide variety of materials, including such materials as pyrylium dye salts including thiapyrylium dye salts and selenapyrylium dye salts disclosed in VanAllan et al. U.S. Pat. 3,250,615; fiuorenes, such as 7,12-di0xo-13-dibenzo- (a,h)fluorene, 5,10 dioxo-4a,11-diazabenzo(b)fluorene, 3,13-dioxo-7-oxadibenzo(b,g)fluorene, and the like; aggregate-type sensitizers ot the type described in Belgian Pat. 705,117 dated Apr. 16, 1968; aromatic nitro compounds of the kind described in U.S. Pat. 2,610,120; anthrones like those disclosed in U.S. Pat. 2,670,284; quinones, U.S. Pat. 2,670,286; benzophenones U.S. Pat. 2,670,287; thiazoles U.S. Pat. 2,732,301; mineral acids; carboxylic acids, such as maleic acid, diand trichloroacetic acids, and salicylic acid; sulfonic and phosphoric acids; and other electron acceptor compounds as disclosed by H. Hoegl, J. Phys. Chem., 69, No. 3, 755-766 (March 1965), and U.S. Pat. 3,232,755.

The amount of sensitizer that can be added to a photoconductor layer to give effective increases in speed can vary widely. The optimum concentration will vary with the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from about 0.0001 to about 10 weight percent or more based on the weight of the coating composition. Normally, sensitizers are added to the coating composition in an amount of about 0.005 to about 5.0 percent by weight of the total coating composition.

The following examples describe the preparation and testing of photoconductive elements. The first example is provided for comparison and describes a photoconductive element which has a slightly roughened surface but contains no matting agent.

EXAMPLE 1 A solution is made consisting of the following:

Grams This composition is coated at 1.0 grams/ft. (dry coverage) on a conducting paper. The coating is then dried rapidly in a moist atmosphere. The moisture in the atmosphere condenses on the surface, producing a blushed or slightly roughened surface. This paper has an average Sheffield Smoothness of 16.

A first sample of this photoconductive coating is coronacharged negatively to 400 volts and then exposed by projection through a microfilm positive. The exposure level is 144 foot candle seconds from a tungsten source. The photoconductive element is then developed in a positive polarity liquid developer of the following formula:

Concentrate: Grams Alkyd resin 1 31.1 Phenolic resin 2 16.0 Hydrogenated rosin 3 0.5 Carbon black 21.75 Blue pigment 2.18 Cyclohexane 176.3

Beckosol resin as supplied by Reichhold Chemical Co.

2 Arnberol S.T. 137 resin as supplied by Rohm and Hans Co.

Staybelite resin as supplied by Hercules Powder Co.

The components are mixed in a ball mill at a pigment to binder weight ratio of 1 to 1.99, obtaining a concentrate containing 28.9 weight percent solids. The concentrate, 2 g., is diluted with 1000 m1. of volatile hydrocarbon solvent for use.

The developed photoconductive element is then passed between squeegee rollers to remove excess developer liquid and a good quality, positive appearing print results. However, it is smooth and different to write on with a pencil.

A second sample of this photoconductive element is positively charged to 400 volts and exposed through a microfilm negative. The same exposure value and source is used as for the first sample. The image development method and material are also the same. The positive appearing image is of poor quality, the toned image being offset and smeared by the squeegee rollers. Also, it is difiicult to write on the photoconductive surface with a pencil.

In the next example, which illustrates a photoconductive element which contains a matting agent in accordance with the invention, the toner smearing and offsetting observed in Example 1 are overcome. Furthermore, the organic photoconductor containing the matting agent produces satisfactory images with either negative or positive charging.

EXAMPLE 2 A coating solution is made as described in Example 1 and in addition, 0.6 gram of poly(methyl methacrylate) beads are dispersed in the solution by means of magnetic stirring. This dope is coated as in Example 1. The resulting photoconductive element has an average Sheffield Smoothness of 100. Prints are made as in Example 1. The positive prints from negative microfilm are much improved over those in Example 1, with essentially no toner offset or smearing. The writability of the photoconductive surface is also improved.

The next example, like Example 1, provides a comparison for the photoconductive elements of the invention, showing results similar to those of Example 1 when a different binder resin is used.

EXAMPLE 3 A solution is prepared as in Example 1 except that Vitel PE 101 resin (a copolyester of terephthalic acid with ethylene glycol and 2,2-bis(4-fl-hydroxyethoxyphenyl) propane, the glycols being in a 9:1 ratio, as supplied by Goodyear Tire and Rubber Company) is used in place of the poly(vinyl-m-bromobenzoate-co-vinyl acetate) binder.

Positive prints from negative microfilm originals have toner smearing and offsetting like Example 1. It is difficult to write on this surface with a pencil.

The next example illustrates a photoconductive element of the invention.

EXAMPLE 4 A paper is prepared as in Example 3 except that 0.6 grams of poly(methyl methacrylate) beads are dispersed in the coating dope. This paper has an average Sheffield Smoothness of 91. When charged, exposed, and developed as in Example 3, the positive print from the negative original has no toner smearing or offsetting. writability is also improved.

The next example is provided for comparison and describes a photoconductive element which contains no matting agent.

EXAMPLE 5 A solution is prepared comprising Grams tDichloromethane 1760 Chlorinated polyethylene 180 1,l-bis(4-N,N-diethylamino-2-methylphenyl)-2- methyl propane 60 4- n-butylamino -2- (4-methoxyphenyl) benzo [b] pyrylium perchlorate 0.72

The above solution is coated at 1.0 grams/ft. (dry coverage) on a conducting paper, dried, charged to 400 volts, exposed, developed and fixed as in Example 1. The resultant print has an average Sheffield Smoothness of 42. Because of this degree of smoothness it is difficult to write on the surface of the photoconductor with a pencil.

The next example illustrates a photoconductive element which contains a polyethylene matting agent in accordance with the invention.

EXAMPLE 6 EXAMPLE 7 A coating dope is prepared of the following:

Parts Dichloromethane Poly(isopropylidenediphenylene carbonate) 9 4,4'-diethylamino-2,2'-dimethyltriphenylmethane 6 2,4-bis(4-ethoxyphenyl)-6-(4-amyloxystyryl)pyrylium fiuoroborate 0.3

Various portions of the resultant dope are admixed with particles of fumed SiO glass or poly(methyl-methacry- TABLE I Size Amount, range, Element No. gm. Composition 1:.

1 Control.

Each element is placed with the roughened photoconductive layer in contact with a smooth surfaced insulating layer carried on a paper support. The receiving elements have a Sheflield Smoothness value of less than about 2. The paper support is in contact with a grounded metal plate. Each such sandwich arrangement is exposed to a negative appearing original. During exposure the conducting electrode of the photoconductive element is biased at about --1800 volts. After exposure, the polarity of bias voltage is reversed to about +1800 volts. The voltage is terminated and the receiver stripped ofi of the photoconductive element. The receiver is then developed using a liquid electrostatic developer. Use of the smooth control element produces an image which exhibits undesirable toning of the background areas; whereas, the images produced using the matte surfaced photoconductive layer show a great reduction in background toning.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be efliected within the spirit and scope of the invention.

I claim:

1. An electrophotographic element comprising (1) an electrically conducting support, and (2) a photoconductive layer comprising:

(a) an admixture of an insulating binder resin and an organic photoconductive compound, which is applied to said support from a solution in a volatile solvent, and

(b) a matting agent in particulate form composed of a resin which is electrically substantially homogeneous with the admixture of said binder resin and said photoconductive compound, said matting agent selected from the group consisting of poly(methyl methacrylate) and polyethylene, which is substantially insoluble in said volatile solvent, thereby retaining its particulate form when applied to said support with the solution of binder resin and photoconductive compound, the surface of said element having a Sheffield Smoothness Value in the range of 45 to 300.

2. An element of claim 1 in which the matting agent has a particle size range from about 0.5 to 50 3. An element of claim 1 in which the matting agent content of the photoconductive layer is from about 0.5 to 30 weight percent.

4. An element of claim 1 in which the matting agent has a particle size range from about 0.5 to 50 and the matting agent content of the photoconductive layer is from about 0.5 to 30 weight percent.

5. An element of claim 4 in which the photoconductive layer has a thickness of 5 to 200 the matting agent particles are in spherical form and the surface of the element has a Shefiield Smoothness Value in the range from about to 200.

6. An element of claim 5 in which the matting agent content of the photoconductive layer is from about 1.0 to 25 weight percent.

7. An element of claim 6 in which the binder resin is poly(vinyl m bromobenzoate-co-vinyl acetate) or polyester and the support is electrically conductive paper.

8. In an electrophotographic process wherein the electrostatic charge pattern is formed and developed, the improvement wherein said pattern is formed using an electrophotographic element as described in claim 1.

References Cited UNITED STATES PATENTS 3,037,861 6/1962 Hoegl et al. 961.$ 3,642,480 2/1972 Vranken 96--1 R 3,281,240 10/1966 Cassiers et a]. 96-1 R 3,634,135 1/1972 Osaka et a1. 961.5 3,502,473 3/1970 Snellman et al 96-67 3,411,907 11/1968 Whitmore et al. 9667 3,097,964 7/1963 Stowell 117161 UB 3,443,946 5/1969 Grabhofer et al 96-67 X 3,079,257 2/ 1963 Morcher et a1. 96-67 3,022,169 2/1962 Heckelmann et a1. 96-67 2,701,245 2/1955 Lynn 26089.5 AW

ROLANDO E. MARTIN, JR., Primary Examiner 

